Many electronic or electromagnetic devices achieve superior performance characteristics when those devices are cooled to very low temperatures. For instance, it is known that some amplifiers will produce little noise if they are cooled to liquid nitrogen temperatures (77 K). Devices incorporating superconducting materials must also be maintained at very low temperatures (generally below 92 K) to maintain their superconducting properties.
In order to maintain the devices at low temperatures, some type of cryorefrigerator must be provided. If a source of liquid nitrogen is available, it may be pumped in coils adjacent the device to provide cooling. Other types of cryorefrigerators are commercially available which pump a fluid in a continuous loop to cool the electronic or electromagnetic devices. In order to minimize the amount of heat from the environment which can be transferred to the electronic or electromagnetic device, an enclosure or cryostat is placed around the device and the cooling coils. Supports are placed in the cryostat which utilize the strength of the cryostat walls to mount the devices inside the cryostats. The cryostats are often evacuated of any gaseous material, thereby reducing convection heating which might occur between the enclosure and the cooled device. Insulation may also be placed inside the cryostat to minimize heat transfer.
When the cryostat is evacuated, it is necessary to design the enclosure to withstand the significant forces which would otherwise cause the enclosure to collapse. Cryostats are, therefore, generally made of a relatively thick metal which has the strength to resist collapsing. The precise thickness required to prevent collapsing depends on the material chosen and the size of the enclosure.
The use of thick-walled structures for cryostats, however, has numerous disadvantages. First, thick-walled structures require a relatively large amount of material, and are therefore expensive. Second, since cryostats are generally made of metal, the large amount of material results in a heavy structure, making it difficult to install or unsuitable for certain applications. Third, the use of such thick material may make working with the cryostat difficult.